So-called “monodose” detergent products are convenient for consumers, since there is no need to measure out the required volume of detergent each time. Various monodose formats, including tablets, and containers made of water soluble material, are already known. Water-soluble containers are attractive since they avoid direct consumer contact with the detergent contents which are potentially irritant, can have a faster dissolution profile than tablets (because the detergent contents do not need to be compacted particles), and can enclose a wide range of different types of detergent ingredients including solids, liquids and gels. With multi-compartment containers, more than one type of composition can be incorporated (e.g. one solid and one liquid composition), incompatible ingredients can be kept separate until use, compartments can be designed to release their respective contents at different times in the wash, and/or greater opportunities for improved aesthetics are provided.
Anionic surfactants are a major component of soaps. However, automatic dishwashing processes are sensitive to the inclusion of foaming ingredients, like anionic surfactants, because the spray action of dishwashing machines is capable of creating a lot of foam which can overflow the machine. Therefore, the skilled person generally tries to use a low level of, or no, anionic surfactants in automatic dishwashing detergents. Instead, non-ionic surfactants are commonly included in automatic dishwashing (“ADW”) compositions; they can provide a detergent and rinse aid function. A wide range of different surfactants are available, some in the solid state at room temperature and some in the liquid state at room temperature.
In practice in the ADW field, the choice of available sizes and shapes of monodose products is limited by the size and shape of machine dispensers into which they are to be placed. There is also a general demand in the art for more concentrated products which use less packaging and/or confer better performance by including higher amounts of active ingredients. It would therefore be useful to have an ADW detergent composition containing a high level of non-ionic surfactant.
Liquid ADW compositions containing high levels of liquid non-ionic surfactant are known, as are solid ADW compositions containing relatively high levels of solid non-ionic surfactant. However, gel formats are visually very attractive to consumers, especially transparent or translucent gels. In addition, liquids and low viscosity gels are liable to leak out of a container if the container material becomes damaged, so self-standing gels would be desirable in this context. In principle, liquid non-ionic surfactants can be gelled using a suitable gellant and solvent, and liquid systems containing dissolved or dispersed solid non-ionic surfactants can also be gelled, but it is a great challenge to formulate a gel which contains a high level of the surfactant, which is self-standing and which is not opaque. For instance, aggregations of surfactant molecules in the gel on the macroscopic scale can scatter light. Dilution of the surfactant content in the gel might help render it more transparent, but would be counter to one of the other technical aims of the formulator.
A further factor is that, when dealing with containers made from water soluble material, it is important to ensure that this material does not dissolve or deteriorate prior to the intended usage point of the container. Adverse interactions between the container material and the container contents during storage can potentially lead to container deformation, loss of mechanical strength of the product and it being rendered unattractive. For this reason it is helpful for the detergent formulation inside the container to have a low water content, or at least a low free water content, otherwise the containers may be liable to soften or crack over time. When space is an issue, it is also important to minimise the levels of carriers not contributing to performance in the wash, such as water.
WO2012/027404 discloses an automatic dishwashing product in which a polyvinylalcohol pouch encloses a “solid gel” formulation of high viscosity at room temperature, which is said to be layered directly on top of a powder detergent formulation. The solid gel formulation contains 76% dipropylene glycol, 19% water and 5% sodium stearate. The stearate is said to be added to create structure. The opacity or otherwise of the gel is not discussed. This gel does not contain any non-ionic surfactant, and so the detergency performance of the gel is thereby significantly impaired. In addition, the high water and dipropylene glycol content is disadvantageous for pouch stability. Although lower water levels and the optional inclusion of non-ionic surfactant are mentioned, this document suggests that the inclusion of at least 70% dipropylene glycol is essential. Accordingly, high levels of surfactant could not be included within the scope of this teaching. In addition, there is no mention of whether or not the non-ionic surfactant that is optionally included in the gel is a liquid compound; if high levels of solid surfactant were to be dispersed in the gel, the resulting composition may well be opaque.
WO94/25557 refers to the inclusion of metal salts of stearate in liquid/gel automatic dishwashing detergents as a rheological modifier/thickener, in an amount of up to 2%, but these ingredients seem to be less preferred in this document due to additional processing requirements thought to be needed. There is no discussion of the opacity or otherwise of the composition; also, the surfactant content is relatively low and the water content is high.
There is still a need in the art for a transparent/translucent, self-standing, low water content ADW gel containing high levels of non-ionic surfactant. Such a gel would be advantageous even when not incorporated in a water soluble container.